A color filter is known to be used in color liquid crystal display devices or other display devices. Such color filter is manufactured by forming matrix-shaped partitions, functioning as shielding portions and banks, on a transparent substrate, and then using an ink jet method to apply coloring materials within the partitions, followed by baking at a prescribed temperature, drying, and hardening.
In this conventional color filter manufacturing method, when liquid material is discharged, the liquid material is applied to the extent of accumulating above the height of the partitions on the substrate. When this is baked at a prescribed temperature, dried and hardened, the volume is reduced, and the height of the coloring layer becomes substantially equal to the height of the partitions.
However, in such a color filter, if there is insufficient control of the ink surface level of the discharged ink, the volume of the ink after drying and hardening may be too large, with ink accumulated upwards beyond the height of the partitions on the substrate; or, the volume after drying and hardening may be too small, resulting in a depressed shape.
These differences in the ink surface after drying occur because, even if the quantity and density of the ink are the same, the drying conditions are different. For example, after ink discharge, if drying is performed under high-temperature conditions, the drying advances too rapidly, and there is a tendency for the ink volume to be reduced. Conversely, if dried under low-temperature conditions, the drying is too slow, and the ink volume after drying tends not to be reduced very much.
This variation in the ink surface may also occur among pixels on the same color filter substrate. In particular, variation occurs between pixels on the peripheral portion of the pixel-forming region and pixels in the center portion, and there is comparative uniformity among pixels in the center portion, excluding the peripheral portion. This is thought to be due to the fact that the drying speed in the peripheral portion of the pixel-forming region is faster than in the center portion. Such a difference in ink surface levels on the same substrate causes color irregularities and color tone differences, and is undesirable.
Such problems also occur in other electro-optical devices besides color filters. For example, it is also necessary that the light-emitting layer be formed uniformly among pixels in electroluminescence display devices, fabricated by using an ink jet method to apply an organic electroluminescence light-emitting solution.
Further, because the surfaces of coloring layers and banks are not always flat, when a protective layer is for example formed on the coloring layer and banks in fabricating a color filter, which is used in a liquid crystal display device, the surface of the protective layer may not be flat, and the distribution of the liquid crystal layer may not be flat.
Hence an object of this invention is to provide a color filter and display device in which differences in the quality (volume, surface height, surface flatness, or similar) of liquid material after drying and hardening are suppressed, so that there are no color irregularities, color tone irregularities, or light intensity irregularities.
A further object of this invention is to provide a color filter and display device in which the color filter surface is made smooth, enabling the uniform distribution of a liquid crystal layer formed on the color filter.